What does it mean when the Bible says that an evil spirit was sent by God to torment Saul (reference 1 Samuel 16:14-15)?

In this psalm, we see a discouraged saint lifted up by meditating on the wondrous works of God. The first nine verses vividly describe the depths of despair. But in the tenth verse, we see a decision to remember the blessings of God. The next few verses (v.11-15) meditate on the works of God and the psalm closes with the saint finding God in the depths of the sea. O glorious message of encouragement!

Paul speaks of his desire to preach the gospel as a debtor to all men. He also speaks of the responsibility of all men to respond to the revelation given to them.